Patent application title: MICROBIOLOGICAL REPROCESSING OF BY-PRODUCTS OF BIODIESEL PRODUCTION

Abstract:

An industrial method of reprocessing a mixture of by-products produced
during biodiesel production containing a glycerol fraction and degumming
residue as well as a feed additive, which may be obtained by this method.

Claims:

1. An industrial method of reprocessing by-products of biodiesel
production, characterised in that yeast of the species Yarrowia
lipolytica is cultured on a medium comprising an aqueous solution
containing, as a carbon source, from 20.0 to 70.0 g/l of a mixture
containing glycerol water and degumming residue, at a temperature below
34.degree. C., preferentially from about 28.degree. C. to about
31.degree. C., medium oxygenation in excess of 20% of O2 saturation,
a maintained pH of 2.5 to 7.5, essentially until the exhaustion of the
available carbon source contained in the medium, where the culture is
preferentially maintained in a periodically repeated way, each time
replacing a portion of the cultured broth with a fresh portion of medium
following the end of a production cycle.

2. A method according to claim 1, characterised in that the medium
additionally contains at least one component selected from a group
encompassing: ammonium sulphate, potassium phosphate, magnesium sulphate,
urea, thiamine, sodium hydroxide, yeast extract, corn mash, Chitosan
and/or Acepol, at a rate of 0.5 to 15 g/L medium.

3. A method according to claim 1, characterised in that the carbon source
used consists of a mixture comprising glycerol water and degumming
residue, where the proportion of degumming residue is at least 15%.

4. A method according to claim 1, characterised in that the culture is
maintained at a pH from about 3.4 to about 3.6, preferentially at
3.5.+-.0.1, and termination of the culture is signalised by a pH increase
to 4.5.

5. A method according to claim 1, characterised in that the biomass
produced is spray-dried, at a temperature of about 200.degree. C. at the
input and 90.degree. C. at the tunnel output.

6. A method according to claim 1, characterised in that the culture is
maintained in a volume of about 1000 litres.

7. A method according to claim 1, characterised in that 15 to 36 g/L of
yeast dry mass is obtained from the separated culture broth.

8. A method according to claim 1, characterised in that the biomass
production occurs at a rate of 1.5 to 3.0 g/L⊕h.

9. A method according to claim 1, characterised in that the biomass
production occurs at an overall efficiency of 0.4 to 0.5 g dry biomass/g
glycerol fraction added to the medium.

10. A method according to claim 1, characterised in that the protein
content in the dry biomass is from 30 to 50% by mass.

11. A method according to claim 1, characterised in that w the culture
makes use of the Yarrowia lipolytica SKOTAN strain deposited in the IBPRS
under the accession number KKP 2018 p.

12. A feed yeast containing from 42% to 49.3% protein in the dry mass.

13. A feed yeast according to claim 12, characterised in that the said
protein contains the amino acids Be, Leu, Lys, Met, Cys, Phe, Tyr, Thr,
Trp and Val at a level in excess of 36 g/100 g protein, preferentially
from about 36.6 to about 36.8 g/100 g protein.

14. A feed yeast according to claim 12, characterised in that the content
of the selected amino-acids in the said protein is in the range defined
in Table 3.

15. A use of the Yarrowia lipolytica SKOTAN strain deposited in the IBPRS
under the accession number KKP 2018 p in the reprocessing of by-products
of biodiesel production, where the by-products comprise a mixture
containing glycerol water and degumming residue.

16. A use according to claim 15, characterised in that the biomass
produced is used as a feed additive.

Description:

[0001] The subject of the present invention is an industrial method of
reprocessing the glycerol fraction obtained during biodiesel production,
as well as a new strain of Yarrowia lipolytica particularly suited for
use in this process.

[0002] The production of natural fuel oil components, so-called biodiesel,
basically consists of the production of fatty acid esters from natural
triglycerides, usu. plant lipids, via transestrification. U.S. Pat. No.
2,271,619 reveals a method of converting the glycerides of higher fatty
acids into esters of short-chain alcohols via the addition of a
monohydroxyl aliphatic alcohol with less than five carbon atoms in the
presence of an essentially anhydrous alkali metal hydroxide as a
catalyst. According to this patent, the process should be carried out in
a reactor at a temperature of 86 to 212° F. (from 30 to
100° C.). The amount of alcohol should not exceed 1.75 glycerol
equivalents. The amount of catalyst varies from 0.1 to 0.5% of glyceride
by mass.

[0003] Subsequent patents amend or complement the patent described method.
U.S. Pat. Nos. 2,360,844; 2,383,632; 2,383,580; 2,383,581; 2,383,614;
2,383,633; 2,383,596 and 2,383,599 respectively describe consecutive
variants of the method revealed in U.S. Pat. No. 2,271,619 consisting of:
a) the addition of an acid to the process and a spray-drying phase; b)
distillation of unreacted alcohol; c) evaluation of the effects of a
catalyst--suggestion of a pH range from 5 to 7; d) the use of a partial
fatty acid ester technique; e) reclamation of unreacted alcohol and
acidification of the liquid in order to improve the separation of
glycerol and esters; f) reprocessing of partially reacted glycerides via
various methods; g) further addition of addition of methanol to a
monohydroxyl aliphatic alcohol (mot methanol), in order to improve liquid
phase separation; as well as h) the addition of a solvent in order to
improve phase separation.

[0004] Other patents suggest more extensive modifications and
improvements. U.S. Pat. Nos. 2,494,366; 2,383,601; 3,963,699; 4,303,590;
4,371,470; 4,668,439; 5,399,731; 5,434,279 and 5,525,126 are also largely
based on U.S. Pat. No. 2,271,619. They are respectively related to: a)
the addition of an appropriate amount of acidic catalyst to the alkaline
catalyst; b) readdition of the acidic estrification catalyst; c)
processing under constant temperature and pressure, from vacuum to
atmospheric pressure, d) addition of a second alkaline catalysis stage;
e) addition of a second estrification stage and the removal of the alkyl
ester using an absorbent; f) introduction of a gaseous alcohol; g)
carrying the reaction out at a lower temperature with additional acid; g)
introduction of an improved phase separation method using an acid; as
well as h) the use of a catalyst consisting of a mixture of calcium
acetate and barium acetate.

[0005] Independent of the technology used, the by-product of the
transestrification of glycerides in need of reprocessing is the so-called
glycerol fraction, comprising soluble hydrophilic reaction products,
meaning glycerol unused catalyst as well as remaining fatty acid esters
and other reagents used during further stages of separation of
transestrification products, i.e. phosphoric acid and inorganic salts. In
most industrial biodiesel production processes and/or by-product
reprocessing used at present, the glycerol fraction is in the form of
"glycerol water" containing glycerol at 20%-80%, as well as the
remainders of the technological process such as soap (0-5%), fatty acid
methyl esters (0-5%), methanol (0-1%), monoglycerides (0-6%), ash (0-5%)
and water to 100% volume.

[0006] Another by-product of biodiesel production, which is difficult to
reprocess, is the so-called gum that is formed during the initial
purification and pH adjustment of plant or animal fats for
transestrification, encompassing the use of phosphoric acid. The arising
by-product chiefly contains phosphoric acid residues in conjunction with
fats, proteins as well as other macromolecules present in the fats.
Furthermore, this by-product contains free plant and animal fats at
various concentrations from 0-10%, 0-10% protein, 0-5% ash, 0-1% glycerol
as well as water.

[0007] The reclamation and/or reprocessing of by-products is a significant
problem in the production of biodiesel.

[0008] The goal of the present invention is to deliver a method of easily
reprocessing a mixture of the aforementioned by-products formed during
biodiesel production. A particular goal of the present invention is to
deliver an efficient method of obtaining easily absorbed biomass from
these by-products, of high nutritive quality, which method could be used
industrially in the reprocessing of the glycerol fraction and degumming,
taking into account the varying composition of these fractions depending
on the technological process used for biodiesel production. The biomass
produced should be characterised by a high content of easily absorbed
protein and vitamins, as well as being suitable for use as a feed
additive.

[0009] Unexpectedly, such stated problems have been solved by the present
invention.

[0010] The subject of the present invention is an industrial method of
reprocessing by-products obtained during biodiesel production,
characterised in that yeast of the species Yarrowia lipolytica is
cultured on a medium comprising an aqueous solution containing, as a
carbon source, from 20.0 to 70.0 g/l of a mixture containing glycerol
water and gum from degumming, at a temperature below 34° C.,
preferentially from about 28° C. to about 31° C., medium
oxygen loading of at least 20% saturation with O2, a pH value
maintained from 2.5 to 7.5, until a substantial exhaustion of the carbon
source available in the medium, where, preferentially, the culture is
maintained in a periodical fashion, and a portion of the culture broth at
the end of a production cycle is replaced with fresh medium.
Preferentially, the medium contains at least one component selected from
among from a group encompassing: ammonium sulphate, potassium phosphate,
magnesium sulphate, urea, thiamine, sodium hydroxide, yeast extract, corn
mash, Chitosan as well as Acepol, at rates of 0.5 to 15 g/L medium.
Equally preferentially the carbon source used is a mixture of glycerol
water and degumming residue, where the degumming residue comprises at
least 15%. Preferentially, the culture is maintained at a pH from about
3.4 to about 3.6, preferentially at 3.5±0.1, and culture completion is
indicated by a pH increase to 4.5. The biomass obtained may be
spray-dried, at a temperature of about 200° C. at the input and
90° C. at the tunnel egress. Preferentially, the culture is
maintained in a volume of at least 1000 L. In a preferential embodiment,
the drawn-off culture broth results in 15 to 35 g/L of dry yeast mass,
biomass production occurs at a rate of 1.5 to 3.0 g/Lh or with an overall
efficiency of 0.4 to 0.5 g dry biomass/g glycerol fraction added to the
medium, whereas dry mass protein content varies from 30 to 50% by mass.
The culture may make use of the Yarrowia lipolytica strain SKOTAN
deposited in the IBPRS under the accession number KKP 2018 p.

[0011] The Yarrowia lipolytica SKOTAN strain has been deposited in the
deposit bank working in accordance with the treaty of Budapest and
maintained by the Instytut Biotechnologii Przemyslu Rolno-Spo ywczego
(henceforth IBPRS), ul. Rakowiecka 36, 02-532 Warszawa and has been given
the accession number KKP 2018 p. This is a wild-type strain, which has
been selected from among many strains of this species belonging to the
collection of the Uniwersytet Przyrodniczy of Wroclaw tested during the
research on the present invention. The selection criteria chiefly
consisted of the culture conditions on a medium based on the glycerol
fraction. First of all, with this strain of the yeast Yarrowia
lipolytica, it was possible to achieve a particularly preferable biomass
production efficiency as well as a considerable tolerance of deleterious
culture conditions such as increasing osmotic pressure as well as a
relatively low pH in the medium. Due to this, the culture process is much
simpler since there is little risk of it becoming contaminated by other
microorganisms. At the same time, the biomass produced possesses
preferential nutritive quantities such as a high content of easily
absorbed protein and vitamins, particularly of the family. Due to this it
can be used as a high-quality feed additive.

[0012] The subject of the present invention is also a feed yeast
containing from 42% to 49.3% protein in dry mass. Preferentially, the
total content of the amino-acids Ile, Leu, Lys, Met, Cys, Phe, Tyr, Thr,
Trp, and Val is over 36 g/100 g protein, preferentially from about 36.6
to about 36.8 g/100 g protein. Equally preferentially, the content of the
selected amino-acids in the said protein is in the range defined in Table
3.

[0013] The next subject of the present invention is the use of the
Yarrowia lipolytica SKOTAN strain deposited at the IBPRS under the
accession number KKP 2018 p in the reprocessing of by-products of
biodiesel production, where the by-products comprise a mixture of
glycerol water and degumming residue. Preferentially, the biomass
produced is used in feed production.

EXAMPLE 1

[0014] Basic medium composition (Medium 1) for the production of biomass
of the yeast Yarrowia lipolytica on a medium based on the glycerol
fraction from biodiesel production (g/litre):

[0015] The above proportions of medium components (Medium 1) should be
weighed for a volume of 1100 L and brought to 1000 L with tap water.

[0016] In certain cases, as appropriate to the production goal (i.e.
contraction of the growth time, protein maximisation, optimalisation of
the amounts and composition of amino-acids or dry mass, etc.) the medium
should be supplemented with other components for enriching or regulating
the process, such as those given as examples in Table 1 below:

[0017] The content of foreign mineral or biological substances (i.e. heavy
metals, toxins, etc.) in the raw materials used in the production should
not exceed that allowed for feed products described in appropriate norms
and regulations.

[0018] After completely dissolving the medium components, they are poured
into the bioreactor, and 100 L of cultured yeast cells are added from a
bioreactor with a 150 L working volume, cultured as above.

[0019] Culture conditions for various strains of the yeast Yarrowia
lipolytica:

the culture should be maintained at a temperature of 25-35° C.
(preferentially about 30° C.±1), at an agitation rate of
400-1200 RPM (preferentially about 700-800), an aeration rate of 0.2-4 L
air/1 L medium/min. (preferentially about 1-1.5 L air/1 L medium/min.).
The pH should be maintained automatically using 10N NaOH. If copious
foaming occurs, a defoamer such as ACEPOL or another should be used.

[0020] Process control using a PH-STAT is based on the regulation of the
pH of the feed yeast culture production medium. The regulation consists
of the monitoring of culture medium pH during yeast production. The
control apparatus maintains a pH of 3.5 with oscillations from 3.4-3.6.
An initial pH of 3.5 is an absolute requirement and is achieved via the
addition of sodium hydroxide. The stabilised pH level limits the growth
of undesirable bacterial flora and makes it possible to obtain a
homogenous culture of Y. lipolytica without other yeasts and bacteria.

[0021] A pH increase above and beyond 4.5 means the termination of the
yeast production process and is evidence of the exhaustion of all of the
available nutrients in the medium.

[0022] The next significant culture parameter is the medium temperature.
The temperature should not exceed 34° C. The optimal temperature
of the reaction mixture is 28-31° C.

[0023] Culture oxygenation is also a significant parameter. Oxygenation
should exceed 20% O2 saturation. Such an oxygenation index may be
obtained through the use of a bioreactor with a FRINGS-type aerator (a
FRINGS turbine). The oxygenation level affects the culture efficiency as
well as yeast cell morphology. Full oxygenation results in yeast as shown
below in FIG. 1. Insufficient aeration of the medium results in mycelia
of Y. lipolytica (FIG. 2).

[0024] The culture should be maintained until the exhaustion of the
available carbon source (here glycerol) in the culture medium. 200 L of
the cell suspension should be left into which the medium components
(Medium 1) should be weighed off for a total volume of 1100 litres, and
900 litres of water should be added. Such a culture method (periodic and
repeated) may be carried out from 5 to 15 times.

[0025] This yeast propagation process makes it possible to obtain 15-35
g/L (preferentially about 33 g/L) of yeast dry mass at a rate of 1.5-3.0
g/lh (preferentially about 2.5 g/l⊕h), with an overall efficiency of
at least 0.4-0.5 g yeast dry mass/g glycerol fraction, (preferentially
about 0.60 g/g in the case of the Yarrowia lipolytica SKOTAN strain).

[0026] The dry yeast protein content varies from 30 to 50%. Using the
Yarrowia lipolytica SKOTAN strain, a yeast dry mass protein content of
about 42% was achieved for the basic medium composition (Medium 1)
described above, as well as from 42% to 48.6% for various additional
medium variants described in Table 1 above.

[0027] Measurements of amino-acid content (expressed in grams per 100
grams protein) obtained from cultures of the Yarrowia lipolytica SKOTAN
strain on various medium variants described above are shown in Table 2
below in conjunction with 1998 FAO-WHO requirements for reference
proteins.

[0028] The biomass produced may be further processed, such as through
drying using known methods, in particular spray-drying, and then
apportioned for distribution and used as a high-quality feed additive,
particularly for use in bovine and chicken feed. Condensation of the
yeast suspension for spray drying was performed using the following
methods: flocculation using Chitosan, microfiltration, centrifugation in
a filtration centrifuge. The condensation level depends on the type of
spray-dryer. Drying should be performed at a temperature of 200°
C. at the input and 90° C. at the tunnel output.

[0029] The yeast is in powder form, with a specific smell and a
beige-brown colour.

EXAMPLE 2

Production of Feed Yeast on a Medium Containing the Glycerol Fraction
(Glycerol Water) as Well as Degumming Residue

[0030] Production is carried out as in Example 1, with the difference that
instead of the glycerol fraction, the medium was supplemented with an
analogous quantity of raw glycerol water and degumming residue at
arbitrary proportions. Optimal mixtures contain degumming residue at 15%
to less than 100% of the mentioned mixture added to the medium. The most
preferential culture results were obtained using full aeration and a pH
maintained at 3.5±0.1 during culturing. Conditional to the use of such
a mixture is the use of an appropriate aeration level and method of
agitation in the reactor (the use of turbines instead of frame mixers).

[0031] The protein content in Yarrowia lipolytica dry mass varied from 42%
to 49.3% in multiple replicants, depending on the compounds added to
enrich the mixture, as listed in Table A. The results of amino-acid level
measurements (expressed in grams per 100 grams protein) obtained in yeast
cultures of the Yarrowia lipolytica SKOTAN strain on various medium
variants containing glycerol water and degumming residue is shown in
Table 3 in conjunction with the 1998 FAO-WHO reference requirements for
reference proteins.